Various flocculants including inorganic materials such as ferric chloride and synthetic polymers such as polyacrylamide flocculants have been employed depending on the purpose of the use. However every known flocculant has some disadvantages. For example, an acrylamide monomer from which the polyacrylamide flocculants are produced has an intense toxicity, which causes some troubles from a viewpoint of safety. Namely the process for the production of these flocculants might be dangerous. Further these flocculants might be contaminated with said monomer. The use of ferric chloride as a flocculant in activated sludge might restrict the application of the obtained sludge as a fertilizer. Furthermore the combustion of the sludge thus treated might be harmful and the disposal of the same might be accompanied by residual toxicity. Polysodium acrylate, which is an anionic flocculant, can be applied only in a limited range and is unavailable in flocculating, for example, microorganisms.
Conventional natural polymer flocculants such as chitosan, guar gum, sodium alginate and CMC are disadvantageous because of the limited flocculating capabilities, though they are free from problems such as toxicity and environmental pollution accompanying their disposal.
On the other hand, an increasing demand for flocculants has made it urgently necessary to develop a flocculant which is available for various matters to be flocculated under various conditions including temperature, pH value and the presence of inhibitory materials and which is accompanied by neither toxicity nor disposal problem.
In order to obtain a flocculant satisfying the above requirements, we previously examined various microorganisms. Consequently we found that an imperfect fungus I-1 isolated fromhumus soil in Wakayama, Japan, accumulated a flocculant, which proved to be completely novel substance and was named PF-101, in a culture filtrate, thus completing the previous invention (cf. Japanese Patent Publication No. 12639/1981).